working with datagrid having 3 radio buttons on same row (in C#)

Question

WPF visual studio 2010 C#

how can I perform these tasks.(XAML or code behind)

I have three columns on the same row of the datagrid,each column contains a radio button named none,read,write.

there is a DEFAULT rule: the write(radio) must be ON when the other two are OFF.

when I turn ON one the other two should turn OFF then if I turn OFF the one that is ON then the default radio (write) should turn ON.

sample:

none read write OFF OFF ON <---- DEFAULT STATE --- ON OFF OFF OFF ON OFF OFF OFF OFF <---- NEVER (see rule)

thanks in advance for your help